Intra-plant variation, varietal difference and heritability of stomatal Lrequency were studied in barley. Stomatal frequency on leaf decreased from flag (L₁) to lower leaves. Stomatal frequency on L₁ sheath was comparable to that on L₄ leaf. Total stomata of awns on one head, estimated from the number of awns per head and the number of stomata per awn, and total stomata on L₁ sheath were about as many as those on upper and lower leaf surfaces of flag leaf (Table 3). Cultivars of high stomatal frequency on flag leaf showed higher stomatal frequency on the other leaves and sheaths compared with those of low stomatal frequency on ffag leaf (Fig. 2). Correlation coefficients between stomatal frequency on flag leaf (lower surface) and those on the other leaves or sheaths were high (Table 5). Stomatal frequency on flag leaf (lower surLace) of 384 cultivars differed significantly, ranging from 43 to 95 stomata per mm². Stomatal frequencies on flag leaf (lower surface) of 7 cultivars grown in two different seasons were highly correlated (r=0. 93) (Fig. 3).

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Researchers, who studied inheritance of growth habit in wheat, did not pay much attention to the presence of intermediate types. They simply divided their materials into two classes, spring and winter. However, a wide range of vernalization requirement was found to exist among wheat cultivars. Therefore, this experiment was performed to get information on the inheritance of intermediate growth habit, particularly, on the possibility of getting non-segregating intermediate types from a cross between typical spring and typical winter wheat. In this experiment, F₂ plants which have different decrrees of intermediate growth habit were obtained from a cross between spring and winter wheat. Non-segregating lines were selected from later genelatlons to ascertain segregation patterns and to get non-segregating Iines differing in vernalization requirement. In F₆, 15 non-segregating lines differing in days to unfolding of the flag leaf were obtained. In F₈, the vernal ization requirements of these lines were tested, and it was ascertained that all the possible classes of vernalization requirement could be obtained as non-segregating lines, covering the full range between the original parents.

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The problem of genetic linkage between an allele to be transferred froni a donor parent and alleles with negative effects on any quantitative trait is investigated theore-tically in relation to sLrccess in backcross breeding programs. A method is outlined for detecting the effect of such linkage. The amount of data required is discussed in terms of the power of the statistical test for the linkage detection. Useful procedureL when linkage is found to be present is also discussed.

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Studies on development in vitro of excised ovaries in the sibmate of diploid Brassica campestris L. ssp. chinensis (L.) Makino cv. Seppaku-taina and in the sibmate of autotetraploid B1'assica campestris L. ssp. pekihelesis (Lour.) Olsson cv. Nozaki-hakusai were carried out. Development in vitro of excised ovaries at four days after pollination was studied in various carbon sources and various sucrose concentrations. Results obtained were as fellows. (1) Seed set in the capsules was observed in culture media with sucrose, glucose, remnose and fructose in each sibmate of diploid Seppaku-taina and autotetraploid Nozaki-hakusai. (2) Neither growth of the capsules nor seed set in the capsules were observed in the medium with mannose in both sibmates. (3) In diploid Seppaku-taina, seed set in the capsules was better in the medium with sucrose or giucose than with fructose or raffilnose. (4) In autotetraploid Nozaki-hakusai, seed set in the capsules was better in the medium with sucrose, glucose or raffinose than with fructose. (5) In the experiment of various sucrose concentrations on development ile vitro of excised ovaries, the higher Sucrose concentration in the medium, the better seed set in the capsules was observed in diploid Seppaku-taina. Seed set in the capsules was best in the medium with 210g/l of sucrose. Percentage of germinated seeds was, however, somewhat less than that from the seed obtained in the medium with lower sucrose concentration. (6) In autotetraploid Nozaki-hakusai, seed set in the capsules was good from 30g/l to 70g/l of sucrose in the medium. (7) Seed set in the capsules in development ile vitro of excised ovaries was different between diploid Seppaku-taina and autotetraploid Nozaki-hakusai.

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A genetic experiment was conducted to detect the multiple allelism of the locus controlling heading time in rice, with the aid of the close linkage with resistance to blast disease. Frve vaneties were used as parents "Fujisaka 5" was early-maturing, "Norin 8" "Toride 1" and "J 287" were medium and "J 315" was late FuJisaka 5 and Norin 8 are Japanese vaneties. The last three lines were developed from the cross between Norin 8 and an Indian variety "TKM.1" by the backcross breedmg program, and they had the Pi-z^t gene for blast resistance that was derived from TKM. 1 (NAGAI et al. 1970). Nine crosses were made between the parents, and the heading date of F₁ and F₂ plants was recorded in the field. The F₃ family of each F₂ plant was tested for resistance to the Ken 53-33 strain of blast fungus to estimate the F₂ genotype for the Pi-z^t gene, , In the six crosses segregating for resistance to Ken 53-33, the Pi-z^t gene was confirmed to control resistance of the hybrid populations (Table 1).

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A factorial experiment on inoculum density of suspcnsion, Ieaf stage of seedlings at inoculation, and host resistance to Philippine downy mildew disease of maize caused by Sclerospora philippinensis Weston was conducted in two trials. Used materials were the two varietal F₁ hybrids, (NE#1XPh9DMR) XMIT VAR2 as a resistant material and La Granja PopcornXUPCA VAR3 as a susceptible one. Concerningr successive changes of number of seedlings with systemic infection, it was possible to differentiate every levels of the three factors. So the expression of resistance to the disease depends upon inoculum density and leaf stage of seedlings to be inoculated. Based on the results obtained here by means of the factorial design experiment in this study, somc discussions on inoculating technique and resistance to the disease in maize were presented.

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Esterase isoenzymes in the leaf blade were observed in a large number of rice strains and hybrid plants between certain parental strains. The slowest isoenzyme band, 1A, was specified by a dominant allele at the esterase locus Est₁ The second band-group, 6A and 7A, was controlled by codominant alleles. Est₂^S and Est₂^F at Est₂, where was also found a null allele. The third band-group, 12A and 13A, was controlled by codo-minant alleles, Est₃^S and Est₃^F at Est₃. Among the three loci, no linkage relation was indicated between Est₁ and Est₂ and between Est₂ and Est₃. These loci involving five dominant and two null alleles are expected to produce twelve zymograms. Among 1, 095 strains of native cultivars observed, eleven out of the twelve expected zymograrns were found and no other pattern appeared. The isoenzymic genotypes well corresponded to conventional varietal groups.

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The response to temperature of the flowering time in rice plants has been studied in order to determine the favourable range of temperature and the lower limit of that. Seedlings of various rice varieties were grown in a phytotron with different temperatures for 14 to 21 days. Varietal responses of flowering time were investigated with different treatnents of temperature to a certain stage of seedlings. (1) Within the range of 30.0-18.6°C, the differences of flowering times between treatments were small in all varieties and this range was considered to be favourable for accelerating flowering time. (2) Between treatments including the range of 18.6-17.5°C, the differences of flowring times of all varieties were large at ear-differentiating stage, though they were small in early growing stage of plants. From this result, the lower limit of the favourable temperature was considered to lie between 17.5 to 18.6°C for all varieties. (3) The temperature lower than 17.5°C appeared to be out of favourable temperature, because the differences of flowering times between the 17.5°C and 13.2°C treatments were also small.

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The present study was carried out in order to clariLy the influence of selection for germinability at low temperature on some agronomic characters in early segregating generations. The local or old variety with higher germinability at low temperature were crossed with a new improved variety with lower germinability and the selection for seed germinability was carried out in the F₃ generation to an extent of 20% in both positive and negative directions. F₄ Strains were grown from the F₃ individuals and divided into two groups based on the presence or absence of selection for grain quality. Yield ability, lodging resistance, plant type and cold resistance were investigated in each strain. First, previous results regarding the genetic mechanisms for seed germinability by the authors were reconfirmed from the continuous variation in the F₃ distributions in which few effective Lactors were analysed by statistical methods. It was also indicated that the selection towards high germinability in F₃ individuals was effective to some extent in the production of strains of high germinability in later generations. Next, the secondary effects for the agronomic characters by selection were investigated in the F₃ and F₄ generations. In F₃ populations, a significant difference was recognized in the rate of white beliverering rices and the awn length between the selected and nonselected groups for quality. There was a tendency in the variance of the character decrease by the selection with the exception of the awn length, although a significant difference was not recognized. In F₄ strains, consistent results were not obtained among characters such as plant type, lodging resistance, grain quality, yield ability and cold resistance. It was shown that the germinability at low temperature was not affected by selection for grain quality. From the results mentioned above, it was demonstrated that the breeding of the promising varieties with the desirable agronomic characters which were characterized by high seed germinability and rapid initial seedling growth under low temperature is possible in direct sowing cultivation in flooded paddy fields in cool temperature regions such as Hokkaido, the northernmost island of Japan.

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